The following descriptions and examples do not constitute an admission as prior art by virtue of their inclusion within this section.
Deposition processes are commonly used in semiconductor manufacturing to deposit a layer of material onto a substrate. Other processes are used to remove layers, define features (e.g., etch), prepare layers (e.g., clean) and dope elements. “Processes” shall be used throughout the application to refer to these and other possible known processes used for semiconductor manufacturing and any reference to a specific process should be read in the context of these other possible processes. In addition, deposition processes may apply to the manufacture of integrated circuits (IC) in semiconductor devices, flat panel displays, optoelectronic devices, data storage devices, magneto electronic devices, magneto optic devices, packaged devices, and the like. As integrated circuit sizes continue to shrink, improvements in materials, unit processes, and process sequences are continually being developed.
Thin film deposition is one method for manufacture of integrated circuits by depositing extremely thin layers of material on substrates or on previously existing layers. Sputter deposition is a physical vapor deposition (PVD) method of depositing thin films by ejecting (or sputtering) material from a target, which ejected material then deposits onto the substrate. Co-sputter deposition is a type of sputter deposition involving more than one PVD gun used to sputter target materials simultaneously to a substrate to provide a particular film composition (e.g., dopant level) on the substrate. Controlling dopant levels in current co-sputter deposition processes may involve using pre-doped targets in sputtering or co-sputtering processes and controlling process power applied to physical vapor deposition (PVD) guns. However, using multiple pre-doped targets to obtain a desired range of film compositions may be prohibitively expensive. Regarding control of process power, in general, providing a low process power results in a thin deposition film, whereas providing a high process power results in a thicker deposition film. However, it is undesirable to rely solely on process power control when attempting to provide a desired dopant level, particularly for very low dopant levels. If the process power is too low, plasma formation may not occur. If the process power is too high, the system may overheat, resulting in cracking or melting of PVD targets.
Collimated physical vapor deposition (i.e., use of a collimator for PVD applications) involves the placement of a single collimator between a target (i.e., the source of the sputtered material) and the substrate to ensure that sputtered atoms from the target arrive at the substrate at angles as close to a normal to substrate surface. Collimated PVD may be used to prevent substantially non-vertical target material flux from reaching a substrate by causing sputtered atoms from the target to impact with portions of the collimator. Such processes have been utilized to provide the seed required for electroplating to fill through-silicon vias (TSV), or improved step coverage of high-aspect-ratio device structures in general. Besides the use of pre-doped alloy targets, there is a need for precise control of film composition (including dopant levels) in co-sputter deposition techniques. Provided herein are systems and methods for control of film composition (including dopant levels) in co-sputter deposition by using collimators.